M20_fever wrote:putting a solid spacer in there wouldn't change the orientation of the u-joints as long as it was the same thickness as the stock disc.

I think the early model coupler is different in the way that it has two u-joints. So when you turn one of them 90* it effects the operation of the u-joints.That's what I've read on the internets anyway. I have no personal experience with those and have never really spent too much time thinking about it.